Our laboratory as well as others has previously noted that sensitivity of lymphocytes to inhibition by prostaglandin (PG)E2 is lost after overnight preincubation. We now show that the change in sensitivity to PGE2 with preincubation varies depending upon the T-cell subset in the culture. In phytohemaglutinin (PHA)-stimulated cultures of fresh cells, PGE2 inhibits proliferation of T cells as well as OKT4 (+) cells and OKT8(+) cells. In PHA-stimulated cultures of preincubated cells, PGE2 slightly augments proliferation of T cells; however, PGE still inhibits OKT4(+) cells and causes marked augmentation of OKT8(+) cells. Thus the "loss in sensitivity" to PGE2 with preincubation is actually a result of the balancing effect of PGE2 inhibiting OKT4(+) cells and stimulating OKT8(+) cells.
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